The West underestimates the growing threat from radical Islam in the Americas.

Oranjestad, Aruba - Regular readers of this column will remember that in July the U.S. asked local officials here to arrest Venezuelan Gen. Hugo Carvajal and to extradite him on suspicion of drug trafficking with Colombian guerrillas. He was detained but the Netherlands stepped in, refused the extradition request and let him go.

The general had been sent here to become Venezuelan consul and spread Bolivarian propaganda. He would have been an important intelligence grab for the U.S. So it wasn’t too surprising that Venezuelan foreign minister Elias Jaua and Cilia Flores, the wife of Venezuelan strongman Nicolás Maduro, celebrated the Dutch decision by meeting his plane when he returned to Caracas.

The third person in the high-level greeting party at the airport—the governor of the state of Aragua, Tareck Zaidan El Aissami Maddah—seemed out of place because he is not in the national government. That is until you consider his résumé: One part master of Middle-Eastern networking, one part honorary Cuban revolutionary, and one part highly ambitious chavista, Mr. El Aissami is a dream come true for Tehran and Havana. That makes him a powerful man in Venezuela.

Although President Obama is being lobbied by left-wing activists to change U.S.-Cuba policy before the next Summit of the Americas in Panama in April, his options are limited by laws that require congressional action to change. But one important decision in his hands is whether to remove Cuba from the U.S. State Department list of state sponsors of terrorism. Before the president does that, Americans ought to learn about allegations by a regional security analyst of Cuba-supported work by Mr. El Aissami on behalf of radical Islam.

The West is well aware of the growing presence of Islamic fundamentalism in the Americas, but policy makers may be underestimating the threat. Joseph Humire is a security analyst and co-editor of “Iran’s Strategic Penetration of Latin America,” a book published earlier this year. In an interview in New York last week, Mr. Humire described Iran’s significant progress, over three decades, in setting up operations in the region.

The earliest stages of the process have featured clandestine operatives using mosques to make connections inside Muslim communities and then using those connections to access wealth and gain political prominence. Where these initial forays have been successful, says Mr. Humire, Iran has opened embassies and established commercial agreements that allow operatives to create businesses, which can be used as fronts for covert operations.

In Venezuela and Bolivia, Iran has moved to the next level, developing a military presence through joint ventures in defense industries. In Venezuela, the state of Aragua, where Mr. El Aissami is now governor, is ground zero for this activity.

Havana applauds this Islamic intervention. Since the rise of chavismo, Cuba has supplied intelligence services to Venezuela and its regional allies, notably Nicaragua, Bolivia and Ecuador. Mr. Humire says it has also supplied passport-information technology to allow these countries to process individuals from the Middle East, hand out new documents and maintain the secrecy of true identities. Cuba has used this capacity to exchange information with like-minded nations, including Russia and Iran.

Raised in Venezuela by a Lebanese-born Muslim father and mentored in the “Utopia 78” left-wing student movement at the University of the Andes, he was Venezuela’s interior minister from 2008-12. According to a June 2014 paper from the Washington-based Center for a Secure Free Society, where Mr. Humire is executive director, “regional intelligence officials” believe that Mr. El Aissami’s office used information technology developed by Cuban state security to give some 173 individuals from the Middle East new Venezuelan identities that are extremely difficult to trace.

The paper, “Canada on Guard: Assessing the Immigration Threat of Iran, Venezuela and Cuba,” says that regional intelligence officials believe that “of the more notable persons of interest” who received false papers from Caracas was Suleiman Ghani Abdul Waked, an important member of Lebanese Hezbollah. The same paper, citing interviews with unnamed Latin American intelligence officials, says Mr. El Aissami has built “a criminal-terrorist pipeline bringing militant Islamists into Venezuela and surrounding countries, and sending illicit funds from Latin America to the Middle East.” Mr. Humire told me the Venezuelan government dismissed the report as U.S. propaganda.

Mr. El Aissami’s Aragua state is where Parchin Chemical Industries (PCI) and Qods Aviation, two Iranian military-owned companies, have joint ventures with Venezuela’s military industry, according to “Iran’s Strategic Penetration of Latin America.” PCI is a maker of explosives, ammunition and rocket propellant for missiles. Qods is a maker of unmanned aerial vehicles. Both companies have been sanctioned by the U.N. Security Council under Resolution 1747.

The chapter written by Mr. Humire says Havana is now “trying to clear its debt to Iran” in order to receive economic assistance from Tehran. This aid will doubtless be conditioned on greater Iranian access to nations under Cuban influence, including Venezuela, he says. They will likely turn to Mr. El Aissami for help.